Recently, displays (such as liquid crystal panel and the like) of a type that does not emit light from the display panel itself that displays a picture have been widely used. In order to provide luminance in a display of this type, a light source is arrayed on the backside of the display panel. In such a display, the most of power is consumed by the light source. Upon this, there has been an idea that can hold down power consumption by monitoring luminance variation of the input picture, detecting a time at which change of luminance is unlikely to be perceived based on the nature of human visual sensation and reducing the luminance of the light source in conformity with the time.
Patent Document 1 discloses a display apparatus that can lower power consumption by reducing luminance in such a degree that it will not cause human to have a strange visual sensation when the image will not produce a significant visual change if luminance is reduced.
FIG. 19 is a diagram showing four displayed image examples different in average luminance level and peak luminance level. A displayed image 101 is one that is high in average luminance level and low in peak luminance level; a displayed image 102 is one that is high in average luminance level and high in peak luminance level; a displayed image 103 is one that is low in average luminance level and low in peak luminance level; and a displayed image 104 is one that is low in average luminance level and high in peak luminance level. In the technology of Patent Document 1, of these images a displayed image having a low average luminance level and a high peak luminance level as displayed image 104, is regarded as a low change image that will not produce a significant change in visual sensation on the display screen even if luminance is lowered, and luminance is reduced when a displayed image of this type is detected.